If your app gets more complex than "Hello World", you will need to create an updated container. To do this, you can use the built-in docker build command because the building gem created a Dockerfile for you. This will take you a fraction of the time that the initial build took because Docker caches your images in stages and most of your image will not have changed at all.

Conclusion

This is just a simple example of how much better the developer tooling around Docker has become over the last year. With Docker 1.0 just around the corner, there has never been a better time to start incorporating it into your daily workflow. If you are ready to get your feet wet with CoreOS, try our Building Your First App on CoreOS tutorial.